By Mar-Vic Cagurangan
Scientists who studied the radiological contamination caused by nuclear tests in the Marshall Islands have detected high concentrations of a "largely ignored" radioactive chemical in the nothern part of the Pacific country.
Preliminary results of the study released by Columbia University found strontium-90 concentrations in ocean sediment samples collected from the test sites.
"Sediment cores from the Bravo test crater in Bikini Atoll and Lacrosse crater near Runit Island (Enewetak Atoll) were assessed for strontium-90 and cesium-137 (137Cs) concentrations, which were found to be measurable in all cores," states a report prepared by Hart I.E.Rapaporta, Ivana Nikolic-Hughesab and Emlyn W.Hughesac, scientists at Columbia University's Center for Nuclear Studies.
"While comparisons to other nuclear sites of interest present a mixed picture, with values both above and below those reported herein, 90Sr/137Cs ratios surpass those of comparable locations," states the report published last month in Science Detect.
The authors said strontium-90 are similar to other radionuclides that descend from the atmosphere after fission and fusion bombs are detonated.
"Once in soil or sediment, it presents a danger to humans because of plant uptake (and eventual conveyance into food sources) as well as atmospheric contamination," the report said.
The scientists, however, said further study is needed to determine the extent of the strontium-90 contamination's potential impact on the Marshallese people who currently live in the poisoned area or may desire to return to their home islands.
The authors noted that strontium-90 is known as a source of major health risk at other contaminated sites, such as Fukushima.
"In the body, 90Sr displaces calcium in bones and teeth and undergoes beta decay into Yttrium-90," the report said. "High levels of 90Sr in the body as compared to calcium have previously been associated with an increased incidence of cancer."
The scientists said large concentrations of strontium-90 can remain in vegetation, soil and sediment for decades.
"Given these findings of continued contamination in many areas of the northern Marshall Islands, we hypothesized that 90Sr content would be measurable as well," the report said.
"These results provide further demonstration of the continuing impact of radioactive fallout on the Marshall Islands and will inform future work to understand how the presence of this isotope might affect current inhabitants (such as through uptake by food sources) and potential resettlement," the report said.
From 1946 to 1958, the United States detonated 67 nuclear weapons in the Marshall Islands. Several scientific investigations have since been conducted to assess the extent of radioactive contamination and associated health consequences resulting from the tests.
"Over the past several years, our team has performed measurements of background gamma radiation, 137Cs concentrations in fruit, and various isotope concentrations in soil and ocean sediment," the scientists said.
They said much of the data from previous studies are now decades old, thus raising "the specter of inaccurate estimates."
"In the case of the Marshall Islands, strontium-90 has largely been ignored in favor of a focus on cesium-137, or radiocaesium," the authors said.
They noted that the Department of Energy's recent report to Congress on the status of the Runit Dome only mentioned strontium-90 in passing, while acknowledging that it is one of the key extant radionuclides in the Marshall Islands.
"Because of the importance of understanding the entirety of the impact of the fallout on the Marshall Islands and the Marshallese people, our data begin to address the issue of 90Sr contamination," the authors said.